Lake Perris is an artificial lake completed in 1973.[1] It is the southern terminus of the California State Water Project, situated in a mountain-rimmed valley between Moreno Valley and Perris, in what is now the Lake Perris State Recreation Area. The park offers a variety of recreational activities. Because of this and the lake's proximity to major population centers, it is very crowded during the summer months.

Day and night, hawks and owls are frequently seen hunting for prey. The bike trail offers an easy and convenient way to see some of the birds and other wildlife of Lake Perris. Early morning or dusk are the best times. Ranger-led hikes are conducted during the spring and early summer months.

Most plants and animals at Lake Perris are well adapted to the hot, dry environment. Chamise leaves are tiny and waxy to minimize water loss due to evaporation. Some grasses and wildflowers rush from bloom to seed in just a few short weeks and are able to complete their life cycle within the brief wet season. Kangaroo rats are so well adapted to dry environments that they seldom drink water, and manage to extract the moisture they need directly from their food.

The plants and animals of Perris valley have changed considerably over the last two hundred years due to human activity, but its natural history can be intriguing.

There are many recreational activities allowed on, in, and around Lake Perris and in the State Recreation Park. Guided hikes are offered on the trail around the lake, and several camping sites are located near the lake side. The lake is open for boating from 6:00 am to 6:30 pm from Thursday to Monday. Other activities include fishing, picnicking, horse-back riding, swimming (in designated areas), and rock climbing. The park also hosts the annual Big Rock Triathlon [2] at sprint and Olympic distances. There is also a museum on the park grounds.[3]

Lake Perris has hot, dry summers and cool, moist winters. Rainy weather is limited almost completely to the months between November and April. The area lies at a crossroads of weather influences. Coastal fog (and smog) comes from the west, while "Santa Anas"—strong, hot dry winds—come from the deserts to the east and northeast. The average water temperature is 70 °F (21 °C) ; during the summer months, it is bathwater-warm and very pleasant to swim in.

For several months following July 2005, the water in Lake Perris was drawn down by about 20 percent (about 24 feet) due to safety concerns with the dam. An extensive modern study concluded that the dam could be partially breached if a 7.5 magnitude or higher earthquake were to strike in the area. Heightening the engineers' fears was the fact that the San Jacinto Fault, easily capable of creating a 7.5 tremor, passes just a few miles north of the lake. It may take two years or more for the state to plan a course of action and bolster the dam.

All recreational activities are still allowed, with some restrictions. Most noticeably, the 35 mph (56 km/h) boating zone has been reduced to the area between the dam and Alessandro Island. The area from the island east is now a 5 mph (wakeless speed) area. Swimming is only allowed at Perris Beach (Lots 1, 2, 3, and 4). Reservations for boats are highly recommended in the summer; weekends sell out fast. Since the drawdown there are fewer first-come first-serve spots available for watercraft. In the summer of 2006 (Memorial Day to Labor Day) most reservations sold out a week or two in advance.